DEOXYGENATION OF HIGHLY HINDERED PHENOLS

Highly hindered phenolic compounds can be efficiently deoxygenated by reduction of the corresponding triflates under homogeneous [RCOOH, Bu3N, PdCl2(PPh3)2, Ph2PCH2CH2CH2PPh2, DMF] or heterogeneous (Pd/C) conditions. Reductive deoxygenation under homogeneous conditions has been shown to occur both in the presence of acid (HCOOH, CH3COOH, (CH3)3CCOOH, PhCH2COOH) or in its absence. The concomitant formation of dibutylformamide apparently derives from aminolysis of DMF by dibutylamine, the Pd(0)-catalyzed hydrolysis product of tributylamine. Deuteration experiments suggest that several hydrogen (or deuterium) sources operate in the hydrogenolysis processes studied. © 1990, American Chemical Society. All rights reserved.